1. Field of the Invention
The present invention relates to a compact and thin high magnification zoom lens.
2. Description of the Related Art
Digital still cameras (DSCs) are widely used as a photographing device. Some DSCs use, a three-group zoom lens of negative-positive-positive refractive powers having a half viewing angle at a wide angle position of 29 to 32 degrees and a magnification of 3×. The three-group zoom lens is widely used because the diameter or entire length of a lens can be miniaturized. In contrast, a typical silver halide single lens reflex uses 35 mm film and has a photographing lens which is changeable but results in a relatively large photographing device to accommodate changing lenses that are separately available in the market. However, a photographing device having a size smaller than 35 mm is in demand. In this case, since the viewing angle is narrow, an exchange lens having a short focal length is needed. Changing lenses, however, introduces the risk of dust or other debris entering the camera and damaging it or degrading performance. Thus, a high magnification zoom lens capable of photographing without changing lenses is desired.
FIG. 1 illustrates a four-group type zoom lens disclosed in Japanese Laid-open Patent Publication No. 2003-241,097. Referring to FIG. 1, the zoom lens includes a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, a third lens group G3 having positive refractive power, and a fourth lens group G4 having positive refractive power, in order from the object side. When the magnification changes from the wide-angle position to the telephoto position, the distance between the first and second lens groups decreases and the distance between the first, third, and fourth lens groups decrease. Also, the first, third, and fourth lens groups move toward the object. Focusing is performed by movement of only the second lens group. Reference numerals in FIG. 1 show surface numbers of each lens. Although the zoom lens has a high magnification of about 10 times, the viewing angle is too narrow.